1. Field of the Invention
The present invention relates to a diffusion furnace used for a semiconductor manufacturing process, and more particularly, to a diffusion furnace having an injector for uniformly supplying a reaction gas into a processing tube.
2. Description of the Related Art
In order to increase the number of chips capable of being produced from a wafer, to thereby reduce the manufacturing costs of a semiconductor device and increase production, the diameter of the wafer is enlarged. Accordingly, an apparatus for manufacturing a semiconductor device must be adapted to the new larger diameter wafer. One such apparatus is a diffusion furnace. In a diffusion furnace, process steps involving silicon oxidation, heat treatment and deposition of impurities are performed. As the diameter of the wafer increases, vertical diffusion furnaces are used more, as opposed to horizontal diffusion furnace.
Referring to the conventional vertical diffusion furnace shown in FIG. 1, the furnace includes a processing tube 1 where a wafer is loaded for performing diffusion, a gas supply conduit 3 for supplying a reaction gas to the processing tube 1, and first and second fuzzy gas supply conduits 9 and 11 for supplying nitrogen gas. The fuzzy gas cleans the inside of the processing tube 1 and reduces the generation of contamination particles.
At one end of the reaction gas supply conduit 3, a U-shaped injector 5 is installed for uniformly supplying a reaction gas to the processing tube 1. On the side of the injector 5, a plurality of fine nozzles 7 are formed at regular intervals for injecting the reaction gas into the processing tube 1.
In order for the gas to react uniformly on the entire surface of the wafer during diffusion in the furnace, the reaction gas supplied through the injector 5 should be uniformly distributed in the processing tube 1. Accordingly, the nozzles 7 formed on the injector 5 should be clean and the openings of the nozzles 7 should be uniformly maintained.
However, since the nozzles 7 are very small, careless finishing processes cause nonuniform nozzle sizes. Also, part of the nozzles 7 can be clogged due to remaining gas or nonuniform pressure of the suppled reaction gas. As a result, the density of the diffused reaction gas on each portion of the wafer is non-uniform, which may occur more frequently as the diameter of the wafer becomes larger.
Even though the injector 5 and nozzles 7 are cleaned by chemicals, the clogging problem still persists because the U-shape of the injector and the small size of the nozzles prevent complete cleaning. Moreover, the U-shaped injector 5 has a complex structure and is fragile.